How to see which Mail Files have an ID stored in them

I need to determine which mailboxes on my server have the user’s ID stored in them. I’m about to rename my whole company to a new Organization due to a company name change.

A substantial number of people use the web client only, so I need to trigger the rename process for them. To do so, I must remove the certificate info from their person document, so the rename will happen automatically. Doing that, however, would cause problems if anyone has stored their ID in their mail file & is using encryption.

Anyone know where I might find a property of the mailfile, person document, or some other notes class I could use to write an Agent to determine who may have stored their ID in their mailfile?